json-builder: do better json number check

If we are going to produce valid JSON we need to do a better JSON number
check because our own float and int parser can accept more variants
and will let through numbers that are not valid JSON.

See #5161

spa/include/spa/utils/json-builder.h

@@ -169,11 +169,13 @@ void spa_json_builder_add_simple(struct spa_json_builder *b, const char *key, in
 		else if (spa_json_is_null(val, val_len) ||
 			 spa_json_is_bool(val, val_len))
 			type = 'l';
-		else if (spa_json_is_float(val, val_len) ||
-			 spa_json_is_int(val, val_len))
-			type = 'd';
 		else if (spa_json_is_string(val, val_len))
 			type = 's';
+		else if (spa_json_is_json_number(val, val_len))
+			type = 'd';
+		else if (simple && (spa_json_is_float(val, val_len) ||
+			 spa_json_is_int(val, val_len)))
+			type = 'd';
 		else
 			type = 'S';
 	}

spa/include/spa/utils/json-core.h

@@ -484,6 +484,44 @@ SPA_API_JSON bool spa_json_is_int(const char *val, int len)
 	return spa_json_parse_int(val, len, &dummy);
 }
 
+SPA_API_JSON bool spa_json_is_json_number(const char *val, int len)
+{
+        int pos = 0, first;
+        /* integer */
+        if (len == 0)
+                return 0;
+        if (pos < len && val[pos] == '-')
+                pos++;
+	first = pos;
+        while(pos < len && val[pos] >= '0' && val[pos] <= '9')
+		pos++;
+	if (pos == first || (first + 1 < pos && val[first] == '0'))
+		return 0;
+        /* fraction */
+        if (pos == len)
+                return 1;
+        if (val[pos++] != '.')
+                return 0;
+	first = pos;
+        while(pos < len && val[pos] >= '0' && val[pos] <= '9')
+		pos++;
+	if (pos == first)
+		return 0;
+        /* exponent */
+        if (pos == len)
+                return 1;
+        if (val[pos] != 'e' && val[pos] != 'E')
+                return 0;
+	pos++;
+        if (val[pos] == '-' || val[pos] == '+')
+		pos++;
+        while(pos < len && val[pos] >= '0' && val[pos] <= '9')
+		pos++;
+        if (pos != len)
+                return 0;
+        return 1;
+}
+
 /* bool */
 SPA_API_JSON bool spa_json_is_true(const char *val, int len)
 {

test/test-spa-json.c

@@ -708,21 +708,39 @@ PWTEST(json_float_check)
 	struct {
 		const char *str;
 		int res;
+		int jsonres;
 	} val[] = {
-		{ "0.0", 1 },
+		{ "0.0", 1, 1},
-		{ ".0", 1 },
+		{ ".0", 1, 0 },
-		{ "+.0E0", 1 },
+		{ "+.0E0", 1, 0 },
-		{ "-.0e0", 1 },
+		{ "-.0e0", 1, 0 },
+
+		{ "0,0", 0, 0 },
+		{ "0.0.5", 0, 0 },
+		{ "0x0", 0, 0 },
+		{ "0x0.0", 0, 0 },
+		{ "E10", 0, 0 },
+		{ "e20", 0, 0 },
+		{ " 0.0", 0, 0 },
+		{ "0.0 ", 0, 0 },
+		{ " 0.0 ", 0, 0 },
+
+		{ "+", 0, 0 },
+		{ "+0", 1, 0 },
+		{ "-", 0, 0 },
+		{ "-0", 1, 1 },
+		{ "-0", 1, 1 },
+		{ "-01", 1, 0 },
+		{ "-00", 1, 0 },
+		{ "-1", 1, 1 },
+		{ "-10", 1, 1 },
+		{ "-.", 0, 0 },
+		{ "-0.", 1, 0 },
+		{ "-01.", 1, 0 },
+		{ "-1.", 1, 0 },
+
+		{ "-.0", 1, 0 },
 
-		{ "0,0", 0 },
-		{ "0.0.5", 0 },
-		{ "0x0", 0 },
-		{ "0x0.0", 0 },
-		{ "E10", 0 },
-		{ "e20", 0 },
-		{ " 0.0", 0 },
-		{ "0.0 ", 0 },
-		{ " 0.0 ", 0 },
 	};
 	unsigned i;
 	float v;
@@ -730,6 +748,9 @@ PWTEST(json_float_check)
 	for (i = 0; i < SPA_N_ELEMENTS(val); i++) {
 		pwtest_int_eq(spa_json_parse_float(val[i].str, strlen(val[i].str), &v), val[i].res);
 	}
+	for (i = 0; i < SPA_N_ELEMENTS(val); i++) {
+		pwtest_int_eq(spa_json_is_json_number(val[i].str, strlen(val[i].str)), val[i].jsonres);
+	}
 	return PWTEST_PASS;
 }